I am using Umbraco 7.2.4.  

I am trying to create a logout button (I know about loginStatus.cshtml, but I am trying to learn how this works).  In the controller I have the following code:

FormsAuthentication.SignOut();
if (Members.IsLoggedIn())
{
  //do something
}
else
{
  //do something else
}

the above code has a true value for Members.IsLoggedIn().  I would have thought the SignOut would set this to false.  What am I not understanding about Members.IsLoggedIn?

if you look at the UmbLoginStatusController, FormsAuthentication.SignOut is used.